1. French-German Research Institute of Saint-Louis, 5 Rue du General Cassagnou, 68301 Saint-Louis, France
2. University of Wisconsin-Madison, Laboratory for Optical and Computational Instrumentation, 1675 Observatory Drive, Madison, Wisconsin 53706, United States
3. French-German Research Institute of Saint-Louis, 5 Rue du General Cassagnou, 68301 Saint-Louis, FrancecUniversity of Bonn, Institute of Computer Science II, Friedrich-Ebert-Allee 144, D-53113 Bonn, Germany